1. Field of the Invention
The invention relates to an electronic control system for an automatic motorized door operating unit to allow a switching safety edge to operate with a motorized door operating unit of the type which is designed for use with a photo eye obstruction detection system.
2. Description of the Related Art
Motorized doors are used for everything from residential garages to industrial moving, rolling or sliding doors and gates. For many years, it has been a best practice and usually a legal safety requirement to provide an obstruction protection mechanism to stop a motorized door moving along a given track when the door has an obstruction that will strike the door if the motor driving the door is not stopped. Many automatic doors or gates, particularly those such doors used in industry, have a door operating unit which controls the power to the door motor to open or close the motorized door along its normal path.
In many cases, light beam sensors such as a photo eye are used to monitor the continuity of an infrared light beam installed across the path of the motorized door so that obstructions to the door can be sensed by the breaking of the photo eye path thereby changing the always on, fail safe control signal which would normally be signaling continuously that the path of the door is not obstructed. A problem with such photo eyes is that they are by inherent design observing obstructions, or the lack thereof, only across the actual path of the light beam from a light emitter to a photo eye on the opposite side of the path. There are other disadvantages to a light beam obstruction sensor as well. Therefore, a moving edge of a door being closed may meet an obstruction that is outside the sensing range of a given photo eye pair therefore causing the door to strike the obstruction whether it is a vehicle, person or other object in the path of the moving door.
Door or gate edge sensors are known devices which are comprised of elongated conductive switches which are contained within an enclosed switch package which can be placed along the entire leading edge of a moving door. Such edge safety switch devices are commonly known as switch safety edges, safety switches, edge switches, switch sensing edges or just sensing edges. The switches operate by being compressed when striking an object thereby shorting parallel flexible conductors within the edge sensing strip to close a conduction loop or path to a control circuit. This action then indicates that the edge has struck an obstruction and therefore the motor should be de-energized.
Edge sensing strips or switches may also have fail safe configurations such that each side of a two-conductor elongated strip is checked for continuity to make sure that any operation of the switch because of an obstruction will actually allow a signal of continuity engagement to be transmitted back to a control module which is monitoring for an opened or closed condition in the edge sensing strip. This presents a continuous signal opportunity much as a photo-eye monitored door so that the motor operator for controlling the door is signaled that the obstruction protection remains operational. Such door operators otherwise default to a safe condition if the operator does not receive a signal from the photo-eye. Likewise, an edge switch must present monitored status by continuity checking in some fashion. Some monitored switching systems are sometimes referred to as 4-wire switches in which simple direct current continuity confirmation is accomplished by simple means. Other monitoring means might include placing a known component, such as a resistor of known value, in the switch edge to facilitate a known or expected measurement of the component, a change if which can be used to signal a change in the switch edge state from functioning to non-functioning.
Conventional, simple photo eye obstruction sensors generate a continuous signal output when no obstructions are blocking the path between light generator and the light beam receiver on the opposite end of the protected path. Photoelectric systems typically use a signal waveform with a designed and controlled amplitude, period and duty cycle, tailored to a particular door operator unit designed to work with a particular controller with a given style of signal output from a given photo eye system. In order to make an edge sensing switch compatible with a given door operator unit which expects to see a signal from the photo eye, a programmable and flexible interface device would be necessary to convert the expected direct current switching information from a 2 or 4-wire safety switching edge to the type of output signal a door operating unit would expect to see if it were observing a simple photo eye across the protected door entrance. Generating a signal expected as output from a functioning photo-eye system based on a retrofitted switch edge device would allow conversion of an existing installation of an automatic door controller which is using a photo-eye obstruction sensor to an edge switch sensor without the need to change the system components. It is also important to accomplish such a conversion utilizing the existing power provided by the motor operator, typically 24 volts for a photo-eye controlled operator.
Accordingly, a device and method is needed in which the user of a motorized door safety sensing system can use edge sensing switch devices to drive a motor controller which normally is expecting to see a digital signal from a compatible photo eye device commonly used in the industry. A system which allows retrofitting of existing door operating units which use conventional photo eye control signaling by providing an interface between the conventional switch sensing edge to the digital control signal emulating the output of a simple photo eye which otherwise would be used with a given control unit to protect from obstructions placed within the pathway of the moving motorized door would allow this and be useful. Such a conversion must maintain the safety conditions afforded by monitoring the operational readiness of the retrofited switch edge when in standby mode.
Accordingly, it is the object of the present invention to provide an interface device which will allow retrofitting a motorized door operating unit from a simple photo eye obstruction sensor to a door edge sensing switch device which uses either a 2-wire or 4-wire continuity control system without changing or modifying the door operating unit already in place.
It is further the object of the present invention to provide a conversion device to change an opened or closed direct current switch condition in a door edge sensing device to a pre-determined digital signal output of a selected amplitude, periodicity and duty cycle to suit a given motorized door operating unit which would otherwise expect to be signaled by a defined digital signal emulating the output of a compatible photo eye sensing device and operate from the existing control voltage provided by the door operating unit.
It is also the object of the present invention to provide a method of retrofitting an existing photo eye type obstruction protection controller to use a door edge switch obstruction protection system without the requirement of changing the controller or applying different power requirements.